Thermostat Monitor

THERMOSTAT MONITOR

The thermostat monitor is designed to verify correct thermostat operation. The thermostat monitor checks for a thermostat that is operating correctly by estimating engine coolant temperature based on calibrated parameters of engine fueling and ambient temperature. The thermostat monitor compares the actual engine coolant temperature to the expected calibrated engine coolant temperature. If the actual engine coolant temperature is not within the calibrated value of the expected temperature, DTC P0128 is set and the malfunction indicator lamp (MIL) is illuminated. This monitor is executed once per drive cycle.